In Situ Chemical Oxidation of VOCs and BTEX Plume in Low-Permeability Soils. Amit Haryani, PE, LSRP

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1 In Situ Chemical Oxidation of VOCs and BTEX Plume in Low-Permeability Soils Amit Haryani, PE, LSRP

2 Process Map Maintenance Yard Diesel, gasoline, solvents Client Goals Attain NJ GWQS - Rapidly Challenges Mixed plume in low perm soil Evolution of CSM Benefits of real time CSM evolution Page 2

3 Process Map Thoughts on Data Interpretation Low perm soils & MIP results Evolution of Remedial Approach Alternate oxidants Results & Path Forward Page 3

4 Site History ,000g Diesel UST 2,000g Diesel UST ,000g Gas UST VOC Storage Bldg Fuel dispenser Wells Installed BTEX; MTBE; TBA Lead TCE; cis-1,2- DCE; VC 1,2-DCA; 1,1- DCE Previous COCs PCE Page 4

5 Initial Conceptual Site Model Hydrogeology Asphalt Brown to grey Silt + med to fine sand, trace clay 0.5 ft 2 ft, occasionally 10 ft Dark grey clayey Silt 90 ft Page 5

6 Remedial Notions - Based on 2008 CSM CHP as remedial approach Site geochemistry preferable for CHP High dissolved iron content Site ph is low (4-6) range Iron a catalyst for hydroxyl radical generation Acidic ph assists keeping iron in solution & available for reaction Site contaminants susceptible to immediate oxidation by CHP Cons: potential TBA (as by-product MTBE oxidation) generation Plus, added benefits : Oxygen generated by hydrogen peroxide decomposition aids aerobic biological systems Site contaminants (TBA, MTBE, benzene, and VC) susceptible to long-term aerobic biological degradation Page 6

7 Remedial Focus EXTERNAL BENCH STUDY 2009 One saturated (8 13 ft bgs) soil sample Groundwater Sample from or adjacent to well with highest concentration MIP-6 and MIP-7) Acidic buffer capacity / Peroxide reactivity / Oxidant effectiveness BENCH RESULTS Initial VOCs: gw 1.5 mg/l VOCs; soil mg/kg Soil ph <4 to start Native iron deemed insufficient; iron addition recommended For all dose ratios: Target COCs degraded in soil & gw For all dose ratios: acetone accumulated; TBA accumulated or same Page 7

8 Recent History 2009 Aug to Sep - Peroxide Injections 2010 Nov MIP / HPT Revise CSM 2011 SPS Injections Page 8

9 Phase I ISCO Application Summary Round 1 August Could not inject target volume (500 gal of 14% H 2 O 2 ) due to surfacing. Reduced H 2 O 2 from 14% to 8% to 4%. Eliminated addition of iron after IP-12. Round 2 September 2009 Used Hydraulic Profile Tool (HPT) on day 1 to establish permeable zones to target injections. Completed injections (IP 17-78) but at reduced target volume (120 gallons). Overall, actual volume <<< target volume.

10 Phase I ISCO Results Summary Tert Butyl Alcohol (TBA) ppb MW-1 MW-5 MW-6 MW-7 MW-10 MW-12 MW-102S MW-103S MW-105S MW-106S Jan-08 Mar-09 Oct-09 Dec-09

11 Phase I ISCO Results Summary Methyl Tert Butyl Ether (MTBE) ppb MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW-105S MW-106S Jan-08 Mar-09 Oct-09 Dec-09

12 Phase I ISCO Results Summary Pechloroethene (PCE) ppb MW-6 MW-8 MW-9 MW-10 MW-11 MW-12 MW-103S MW-105S MW-106S Jan-08 Mar-09 Oct-09 Dec-09

13 Phase I ISCO Lessons Learned Injection volumes restricted Poor performance > 7ft bgs. HPT data clarifies delivery issues. Injections forced to target 5 to 7 feet depth interval. Rapid reaction of Catalytic Hydrogen Peroxide evolves gas = back pressure. Back pressure reduces ability to inject further oxidant solution. Difficult to inject volumes into areas previously injected. Follow up treatment of residual hot spots warranted. Rebound / back diffusion? Permanent injection wells?

14 Phase II Hot Spot treatment Strategy focusing on greatest residual Use MIP/HPT direct sensing to focus Hot Spot treatment efforts Identify zones of flux 2010 Apply different oxidant - SPS Strong oxidizing radical Catalyzed by native iron No temperature increase No off-gas Oxidation & reduced formation of TBA (suggested in lit.) More Persistent Lower affinity for natural soil organics (Brown 2003); greater efficiency Page 14

15 MIP in Low Perm Soil MIP Operator Observations PID readings >11 ft bgs suggestive of mg/l to 10s mg/l conc.? Signal in multiple areas of high soil conductivity Multiple grab samples at depth do not confirm Signal Bias in Low Perm Soil Others (Quinnan, et al) have documented bias in MIP within low permeability units + varying sensitivity depending on chlorine substitution

16 Phase II ISCO Application January 2011 Area 1 23 injection points Catalyst 575-gallon 15% persulfate 1,885-gallon Flow Rate 1 gpm 3.57 gpm 2011 Area 2 42 injection points Catalyst 1,710-gallon 15% persulfate 5,925-gallon Flow Rate 0.76 gpm 3.85gpm Area 3 24 injection points Catalyst 600-gallon 15% persulfate 2,200-gallon Flow Rate 0.58 gpm 2.78 gpm

17 Phase II ISCO Results Summary -TBA MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104S Mar Mar 11-May 11-Aug MW-105S MW-106S

18 Phase II ISCO Results Summary -MTBE MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S Mar Mar 11-May 11-Aug

19 Phase II ISCO Results Summary -PCE MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S Mar Mar 11-May 11-Aug

20 Phase II ISCO Results Summary HOT spot wells = Significant reduction in concentrations MW-5, MW-10, and MW TBA below GWQS in all on-site wells Except: MW-1, MW-5, and MW-10 MTBE below GWQS in all on-site wells Except: MW-10 Off Site contaminant increases MW-104S and MW-106S

21 Next Steps to Site Closure MNA Considerations Anaerobic Past system behavior suggest anaerobic conditions exist(ed) PCE degradation via RD with daughter products and ~50 % reduction of COCs without active treatment over 4 yrs ( 04 08) In fuel release source areas, e-acceptors (e.g., oxygen, nitrate, iron and sulfate) often absent/limited handicapping biodegradation Anerobic biodegradation systems benefit from Fe-SPS once redox potential decreases again as the process supplements iron and sulfate Life Cycle Costs: MNA with LTM vs. Additional ISCO with Re-assessment Given past plume stability (pre-isco perturbations), LTM could be in perpetuity One additional targeted applications of Fe-SPS equivalent to 2 years of LTM Additional ISCO shortens LTM time by years Sequential injection events within target interval = mass reduction in zones of flux.

22 The End Amit Haryani, PE, LSRP Senior Project Manager (732)